So, I read through that page, as well as the one it linked to, and it seems like I need to use plus addressing and then have messages that are flagged forwarded to that address.
The problem that I'm having now, is that plus addressing doesn't seem to be working. I have yet to install the spam/virus filtering packages as per the how-to, but it should still work, right?
What currently happens is that an email sent to jason+Junk@mydomain.com just ends up delivered to the normal inbox. A copy of the directory for that user is as below:
.Drafts/ courierimapkeywords/ cur/
.Junk/ courierimapsubscribed maildirsize
.Sent/ courierimapuiddb new/
.Trash/ courierpop3dsizelist tmp/
Is "jason+Junk" the correct format for this folder setup? Is there some other setting I need to change?